System and method for pasteurizing at least one liquid

ABSTRACT

A system for pasteurizing a liquid product includes at least one liquid component that can be pumped, including a supply container for making the unpasteurized product available, an inlet line for conveying the unpasteurized product, a pasteurization circuit for pasteurizing the product, and an outlet line for conveying the pasteurized product. The pasteurization circuit includes a buffer container for holding the product during a prescribed constant contact time for pasteurization and a fluctuating flow rate of the product through the buffer container.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of and Applicant claims priority under35 U.S.C. §§120 and 121 of U.S. application Ser. No. 13/698,758 filed onNov. 19, 2012, which application is the National Stage ofPCT/CH2010/000129 filed on May 20, 2010, the disclosures of which areincorporated by reference. The international application under PCTarticle 21(2) was not published in English.

TECHNICAL FIELD

The invention relates to a system for pasteurizing a liquid productconsisting of at least one liquid component that can be pumped, with asupply container for supplying the unpasteurized product, an inlet lineand an outlet line for conveying the unpasteurized product, a heatingcircuit for heating up the product to a pasteurization temperature andpasteurization circuit for pasteurizing the product, and a method forpasteurizing the liquid product according to the preambles of theindependent claims.

BACKGROUND

Devices and methods offering solutions for pasteurizing a liquid productconsisting of one or more components are known in the production ofliquid products. Tasks of such systems or methods respectively, comprisethe provision of the liquid product, the pasteurization itself and thesupply of the mixed liquid product to installations for furtherprocessing. Typically, a further processing step consists in filling theliquid product into containers provided for this. For example, a varietyof refreshing beverages, particularly products containing milk, etc. areproduced in the food industry by means of such systems.

The pasteurization of the untreated product plays a central role inensuring the product quality. The pasteurization is a method for which aliquid is heated up for a short period of time and is subsequentlycooled down again, by which most bacteria are killed. For this, it isimportant that the product to be pasteurized remains a certain timeunder the influence of the higher temperature. This time period iscalled “contact time”. It is of e.g. around 30 seconds at 75 to 90° C.After this time the product is again cooled down and is deemed to beharmless for consumption. However, the contact time also depends on thetemperature. In order to take into account this dependence, a variable,the pasteurization unit, has been introduced. It is calculated accordingto the following equation:

PU=t×1,39^((T−60°))

Thereby, t is the resting time in minutes at the temperature T. In orderto reach a reliable pasteurization, a substantially constant number ofpasteurization units shall be maintained. Thus, according to thisequation it is possible to vary the temperature, keeping the contacttime constant, or to vary the contact time, keeping the temperatureconstant, within certain limits, such that PU remains substantiallyconstant.

In order to satisfy this requirement, in known solutions the products tobe pasteurized are guided for the required contact time through pipecoils which are kept hot. Depending on the shape of these pipe devices,like e.g. the number of deviations, the path of the product can beextended or shortened at the constant temperature by means of which thecontact time can be changed. Parallel pipe systems with differentfeatures are also used, wherein the liquid to be pasteurized can beguided either through the one or through the other pipe system in orderto satisfy different pasteurization requirements in the sameinstallation.

On the other hand there are also solutions in case of which thetemperature is varied, however this has the disadvantage that atemperature regulation per se is not efficient and is difficult to berealised because of the inherent inertia of such a regulation,particularly in case of small temperature variations.

Systems using a combination of both described methods are also known.

After the pasteurization the product is e.g. cooled down and transportedfurther. Often, the product which was pasteurized in this way is filledinto a so-called aseptic container, in other words a bacteria-freecontainer, before it is supplied to e.g. a filler device. These fillerdevices are subject to the so-called stop-go principle, i.e. varyingquantities of the liquid product are extracted non-continuously. If thedelivery has to be interrupted, the product is guided back by cooling itdown, as the case may be, and has to be pasteurized again because thebacteria-free state cannot be ensured anymore. If the interruptionexceeds a certain time period, this process has to be repeated, with theresult that the same product has to be heated up and cooled downmultiple times. This can only be done a couple of times, whereafter theproduct is unusable because of thermal stress. The consequence is thatthe system has to be cleaned up by means of water and only after thatnew unpasteurized product can be refilled. This is disadvantageous forthe operators of such systems because they loose on the one handvaluable production time and on the other hand a high quantity of theproduct.

DISCLOSURE OF THE INVENTION

The invention has the objective to provide a system which has a highflexibility in absorbing supply interruptions of the product to aninstallation for further processing. Furthermore, it is an objective ofthe invention to provide a method for pasteurization of liquid products.

This objective is solved by a system for pasteurizing a liquid productconsisting of at least one liquid component that can be pumped. Thesystem comprises a supply container for supplying the unpasteurizedproduct, an inlet line for conveying the unpasteurized product, apasteurization circuit for pasteurizing the product, and an outlet linefor conveying the pasteurized product. The pasteurization circuitcomprises a buffer container for holding the product during a prescribedconstant contact time for pasteurization and a fluctuating flow rate ofthe product through the buffer container.

Furthermore, a method for pasteurizing a liquid product is claimed,consisting of at least one liquid component that can be pumped, forwhich the unpasteurized product is supplied out of a supply containerinto an inlet line, is subsequently pasteurized in a pasteurizationcircuit and the pasteurized product is supplied to an outlet line. Theproduct is supplied to a buffer container in the pasteurization circuitand is held in it during a prescribed constant contact time for thepasteurization and in the presence of a fluctuating flow rate of theproduct through the buffer container. Thus, according to the claims, asystem and a method with a buffer function in the pasteurization circuitare provided. By this, it is departed from the conventional solutionsbased on the use of pipe coils and on a constant transport quantity inorder to maintain the contact time and which imply a temperatureregulation. In case of the present solution the observance of thecontact time is given by the use of the buffer container which canreceive a variable quantity of a product to pasteurize. This regulationis easier to achieve and results in a better energy balance.Particularly, by controlling/regulating the inlet into the buffercontainer and, as the case may be, also by controlling/regulating theoutlet paths out of the buffer container, it is possible to adjust thelevel of the product in the buffer container.

SHORT DESCRIPTION OF THE DRAWINGS

The drawing shows a schematic of an embodiment of a system according tothe invention with corresponding components and their connections.

WAY OF CARRYING OUT THE INVENTION

Further advantageous embodiments of the invention result from thedependent claims and from the embodiment examples described in thefollowing by means of the FIGURE.

The FIGURE shows a preferred embodiment of the system 1 withcorresponding components and their connections.

The components of the system 1 and their connections are described firstand subsequently the path of the product P through the system 1 bytaking into account the special features of the components.

The product P to be pasteurized is filled into a supply container 6.Water W can equally be filled into the container 6. The function of thewater W will be explained later in more detail. The supply container 6is connected to a pasteurization circuit 25, which is indicated by thedashed lines, by means of an inlet line 8 a. A first pump 7, whichpreferably has a variable flow rate, is arranged in the inlet line 8 adownstream of the supply container 6. The actual flow quantity throughthe inlet line 8 a is measured by a flow meter 15, wherein themeasurement result is supplied to a controller 9. In case of deviationsof the actual flow quantity from the target flow quantity, thecontroller 9 controls a first control element 14 which post-regulatesthe first pump 7 in a known way until a correct flow quantity ismeasured. The flow rate may however also be regulated by other means,e.g. by means of a regulating valve arranged downstream of the firstpump 7. A recuperation zone 13 is arranged downstream of the flow meter15, which takes care of a heat exchange of the product flowing throughit. This will be explained in more detail later. A pasteurizationcircuit 25 is arranged downstream of the recuperation zone 13. Itcomprises a first heat exchanger 10, e.g. a plate heat exchanger, whichis coupled to an external heating circuit 16. It is understood that theheating circuit may also be a part of the pasteurization circuit 25.

The construction of a heating circuit 16 is known and is only shortlyexplained here for the sake of completeness. It comprises a transportline for hot water for supplying energy to the first heat exchanger 10,a second heat exchanger 12 which keeps up the heat energy of the hotwater in the heating circuit 16 by means of supplied steam D and a pump11 for transporting the hot water through the transport line.

A buffer container 2 is arranged in the pasteurization circuit 25downstream of the first heat exchanger 10, inside which the mainpasteurization phase takes place, i.e. the storage of the product at atarget temperature for the time period of the contact time. The buffercontainer has a content of e.g. 100 or 300 liters. It comprisespreferably at least one, particularly exchangeable, baffle device forcontrolling the product flow direction, arranged in its interior. Thebaffle device is not shown here because of clarity reasons. Its task isexplained in more detail in connection with the explanation of theproduct path through the system. Furthermore, the buffer container 2comprises preferably at least one insulating layer for thermallyinsulating the content against the ambient, which covers substantiallyentirely its walls and which is not shown here. Preferably, the innerwalls of the buffer container 2 are polished smooth.

A flow meter 3 for measuring the filling level inside the buffercontainer 2 is provided at the buffer container 2. The variable fillinglevel is illustrated by the double arrow L.

A second pump 5 is arranged downstream of the buffer container 2, whichis preferably a pump with variable flow rate. The pump is connected to asecond control element 4, e.g. a motor with a frequency converter, foradjusting the desired flow rate of the pasteurized product P.

The controller 9 is connected to the filling level meter 3 for capturingthe current filling level of the buffer container 2. Furthermore, it isconnected to the second control element 4 in order to capture andcontrol the current flow rate of the product P through the second pump5. The connections of the controller 9 are illustrated by thedashed/dotted lines. They are not shown here exclusively. In fact thecontroller 9 may also be used to capture other parameters of the system1, e.g. the temperature of the product P in different phases.

The second pump 5 is connected to the recuperation zone 13 at the outputof the pasteurization circuit 25. After the recuperation’ zone 13 thepasteurized product is guided into an outlet line 8 b. A firstrefractometer 18 for determining the density of the pasteurized productP is arranged in the outlet line 8 b. Furthermore, a third heatexchanger 20 is arranged in the outlet line 8 b, being used for coolingthe pasteurized product P by means of cooling water K. Downstream of thethird heat exchanger 20 the end product P may be passed on to aninstallation for further processing, e.g. a filler, which is not shownhere. Alternatively, it may be filled into an aseptic container 22, fromwhich it is passed on to the installation for further processing via theline O. A first switch 21 may be provided at the inlet of the asepticcontainer in order to redirect the end product into a disposal line 19in order to be disposed of. A second refractometer 17 is arranged inthis line 19, which measures the density of the end product P to bedisposed of. A second switch 23 is arranged at the outlet of thedisposal line 19, by means of which the discharged end product P mayeither be disposed of in a sewer 24 or may be guided back into thesupply container 6.

Now, the path of the product through the system is described. For thesake of better understanding, temperature values of the product P aregiven, which shall however only serve as examples. Other temperaturevalues are readily possible.

The unpasteurized product P is pumped out of the supply container 6through the recuperation zone 13 by means of the first pump 7. Theproduct P has a temperature of 20° C. before the recuperation zone 13.In the recuperation zone 13 it is heated up strongly and has atemperature of already 85° C. at the exit of the recuperation zone 13.It is heated up more to the required pasteurization temperature of 90°C. by means of the first heat exchanger 10 and thereafter it gets intothe buffer container 2. Because of the insulation of the buffercontainer 2 the product keeps its temperature of 90° C.

In the buffer container 2 the product particles follow the path to theoutlet of the buffer container 2 and are pasteurized during this contacttime. During the passage from the inlet of the buffer container 2 untilits outlet it is desired that a piston flow is present in order to makesure that substantially all particles of the product P remain in thebuffer container 2 for the duration of the same contact time. The usageof the buffer container 2 has a further advantage because of itsconstitution; the flow inside it is less turbulent than inside pipecoils, in case of which turbulence is generated at each deviation.However, the already described at least one baffle device is used tofurther reduce turbulences. It can e.g. be a mesh by means of which thedirection of the velocity vector of the particles flowing through themesh are parallelized and the majority of them point in the direction ofthe outlet of the buffer container 2. The mesh may be dimensioned to befine or coarse depending on the consistency of the product and ispreferably exchangeable in this sense.

After passing through the buffer container 2 the pasteurized productexits the buffer container 2 and is transported into the recuperationzone 13 by means of the second pump 5, still having a temperature ofalmost 90° C. The path of the pasteurized product P in the recuperationzone 13 is illustrated by the dashed line. Because of the energy balancethe product has a temperature of 25° C. at the exit of the recuperationzone and the entrance into the outlet line 8 b. This is known and is notexplained here in more detail.

Subsequently, the pasteurized product P is guided into the third heatexchanger 20 and is cooled down to a desired end temperature therein.Finally, the cooled down, pasteurized end product P is transported intothe aseptic container 22 and further into the device for furtherprocessing. This type of filling is called “aseptic cold-filling”.

Alternatively to the cold-filling (aseptic cold-filling), the presentinvention can amongst others also be used for a so-called “hot-filling”which is not shown here. In case of this hot-filling the still warm,pasteurized product P is directly filled, such that the third heatexchanger 20, the recuperation zone 13 and the optional asepticcontainer 22 are obsolete.

As already described, the quantity of the unpasteurized product P pertime unit flowing out of the inlet line 8 a into the pasteurizationcircuit 25 and into the buffer container 2 is regulated by means of thefirst pump 7 arranged downstream of the supply container 6 and thedelivery quantity of the pasteurized product P per time unit isregulated by the second pump 5 of the pasteurization circuit 25, whichis arranged downstream of the buffer container 2. By the interaction ofthe first and the second pump 7, 5 an efficient level regulation can beachieved inside the buffer container 2, such that on the one hand thecontact time in the buffer container 2 can always be maintained and onthe other hand the delivery quantity of the pasteurized product P can beadjusted to the requirements of the device for further processing. Thisinteraction is controlled and adjusted by means of the controller 9which calculates the required delivery quantity per time unit, whichshall be fed out of the inlet line 8 a into the pasteurization circuit25 and which shall be supplied out of the pasteurization circuit 25 intothe outlet line 8 b, depending on at least one parameter. This parametermay e.g. be the filling level in the buffer container 2. The fillinglevel in the aseptic container 21 can be used as a further parameter.Other parameters, e.g. an extraction rate of the end product P from theaseptic container, etc. are also possible. It is understood thatindividual parameters or a combination of parameters can be used. Afterthe calculation by the controller 9 the required product quantity pertime unit for the first and the second pump 7, 5 is adjusted by means ofthe respective control element 14, 4.

A special operation case arises in case of a stop of the supply of theend product P to the device for further processing. This is a frequentoperation case and therefore has to be taken into consideration for apasteurization system. Such a stop may arise e.g. by interruptions inthe installation arranged downstream of the pasteurization system, e.g.filler or labelling machine, because of changes in the filling rate.

In case of known solutions with a constant product throughput theproduct has to be guided back into the supply container in such a case.The alternative would be to dispose of the product until the entirecircuit has been pumped out. However, this would lead to a too highwasting of the product, particularly because in many cases the deliverystop is of short duration. Because of this, the product is guided backand mixes with the still unpasteurized product present in the supplycontainer 6. After a new delivery start the portion of the product whichhas been guided back is pasteurized once more. In case of multipledelivery stops it is possible that the product has to be pasteurizedseveral times, with the result that it looses its quality and cannot beconsumed anymore. The consequence is that the pasteurization system hasto be entirely emptied and the contents have to be disposed of. Thepractice shows that this case occurs regularly. By this, the operatorfaces high costs which have to be avoided or minimized.

In case of the present invention this undesired effect is at leastminimized because a certain duration of the delivery stop can be bridgedbecause of using the buffer container 2. It is only when this durationhas lapsed without a production restart that the product has to beguided back. Consequently, the number of times the product is guidedback and pasteurized again is reduced, with the consequence that theentire emptying of the pasteurization system 1 can in many cases beavoided.

After a stop of the delivery of the end product to the installation forfurther processing, a stop or a reduction of the delivery of thepasteurized product P out of the pasteurization circuit 25 is triggeredby the controller 9. After stopping the delivery of the end product Pthe supply of the unpasteurized product P into the buffer container 2 isadditionally reduced to a minimum product quantity per time unit. Theminimum product quantity per time unit may e.g. be in the range of about10% of the nominal throughput quantity of the product P. However, othervalues are also possible. After reaching a maximum filling level of thebuffer container 2 and/or of a maximum stop time the supply into thebuffer container is completely stopped by the controller 9.

The transport of the product P can however be restarted after stoppingthe delivery of the end product for an allowable interruption time ofthe delivery of the end product. It is only after the interruption timehas elapsed that the product is disposed of from the inlet line 8 a, thepasteurization circuit 25 and the outlet line 8 b in case of the“aseptic cold-filling”. This is done by supplying water W into thesupply container 6 and pumping the water W into the inlet line 8 a,further into the pasteurization circuit 25, further into the outlet line8 b and finally into the disposal line 19. The instant of the completedisposal is measured by the second refractometer 17. In case of the“hot-filling” which is not showed herein, a heat exchanger for coolingdown the product to be disposed of would be arranged in the disposalline.

A further advantage of the invention consists in that the allowableinterruption time can be significantly extended, in case of stopping thedelivery of the end product, because of the reduction of the quantity ofthe unpasteurized product P which is supplied into the buffer container2 to a minimum product quantity per time unit. For example, aninterruption time which is ten times longer is possible in case of areduction of the product quantity to 10% of the nominal throughputquantity. In other words the buffer time until the system has to beentirely emptied extends.

When the operation of the pasteurization system 1 is restarted, thefirst refractometer 18 measures the density of the liquid flowing in theoutlet line 8 b, with the consequence that the instant of the readinessfor operation and of the possible re-delivery of the end product can bedetermined.

The present invention allows an increase in flexibility during thepasteurization, particularly in case of the stop-go operation of abeverage production system, by using an active buffer for the product tobe produced and a significant saving of the product in case of operationfailures. Furthermore, the production quantity can be adjusted to therequirements because of the variably adjustable throughput quantity ofthe product.

Although advantageous embodiments of the invention have been shown anddescribed, the invention is not restricted thereto but it may beexecuted and applied in other various ways within the scope of thefollowing claims.

LIST OF REFERENCE NUMERALS

-   1=pasteurization system-   2=buffer container-   3=filling level meter-   4=second control element-   5=second pump-   6=supply container-   7=first pump-   8 a=inlet line-   8 b=outlet line-   9=controller-   10=first heat exchanger-   11=pump of the heating circuit-   12=second heat exchanger-   13=recuperation zone-   14=first control element-   15=flow meter-   16=heating circuit-   17=second refractometer-   18=first refractometer-   19=disposal line-   20=third heat exchanger-   21=first switch-   22=aseptic container-   23=second switch-   25=pasteurization circuit-   D=steam-   P=product-   O=outlet of the end product-   K=cooling water-   L=filling level in the buffer circuit-   W=water

What is claimed is:
 1. A system for pasteurizing a liquid productcomprising at least one liquid component that can be pumped, the systemcomprising a supply container for supplying the unpasteurized product,an inlet line for conveying the unpasteurized product, connected to thesupply container, and connected to a heat exchanger configured to heatthe liquid product in the inlet line, a pasteurization circuit forpasteurizing the product and connected to the inlet line, and an outletline for conveying the pasteurized product and connected to thepasteurization circuit, wherein the pasteurization circuit comprises abuffer container for maintaining the product during a contact time forpasteurization and a fluctuating flow rate of the product in the buffercontainer.
 2. The system according to claim 1, wherein the quantity ofthe unpasteurized product per time unit flowing out of the inlet lineinto the pasteurization circuit into the buffer container is regulatedvia a feed pump arranged downstream of the supply container, and whereinthe feed pump has a variable flow rate.
 3. The system according to claim1, wherein the pasteurization circuit comprises a removal pump arrangeddownstream of the buffer container, having a variable flow rate, and forregulating the delivery quantity of the pasteurized product per timeunit out of the buffer container into the outlet line.
 4. The systemaccording to claim 1, wherein a filling level meter is provided formeasuring the filling level inside the buffer container.
 5. The systemaccording to claim 1, wherein the buffer container comprises, arrangedin its interior, at least one, particularly replaceable, baffle devicefor controlling the product flow direction.
 6. The system according toclaim 1, wherein the buffer container comprises at least one insulatinglayer for thermally insulating it from the ambient, which surrounds itswalls substantially entirely.
 7. The system according to claim 1,wherein a controller is provided for calculating the required productquantity per time unit to be supplied out of the inlet line into thepasteurization circuit and out of the pasteurization circuit into theoutlet line depending on at least one parameter.